Abortion Teaching Does Not Meet the Definition of Infallible Teaching
In addition, the popular notion that whatever the pope says on a serious topic is infallible is an exaggeration of the principle of infallibility. While some ultra-conservative groups claim that the teaching on abortion is infallible, it does not in fact meet the definition of an infallible teaching. Since the doctrine of papal infallibility was first declared in 1870, only three teachings have been declared infallible: the Immaculate Conception of Mary; the Assumption of Mary; and the declaration on infallibility itself.
At the heart of church teachings on moral matters is a deep regard for an individual’s conscience. The Catechism states that “a human being must always obey the certain judgment of his conscience.” Catholic teaching holds that when the church cannot speak definitively on a matter of fact, the consciences of individual Catholics must be primary and respected. This leaves latitude for Catholics to support prochoice politicians.
Sign up for the OV Daily Newsletter
OV Social
In your reasoning you have stated that “a human being must always obey the certain judgment of his conscience.” You also said that when the church cannot speak definitively on a matter, "the consciences of individual Catholics must be primary and respected. This leaves latitude for Catholics to support prochoice politicians."
Your reasoning is flawed for two reasons:
The church has taught on a matter of faith and morals that abortion is a grave and mortal sin. The church has also taught that supporting these policies are wrong. Therefore the church has spoken definitely on the matter.
Secondly, in your support of deferring to a person's conscience you have failed to mention what the Catechism speaks of in terms of malformed consciences. The church clearly teaches that this ignorance, which includes defiance of church teaching, is no excuse for sins commited. This is from CCC 1790 - 1792. I have provided an excerpt for reference:
Yet it can happen that moral conscience remains in ignorance and makes erroneous judgments about acts to be performed or already committed.
This ignorance can often be imputed to personal responsibility. This is the case when a man "takes little trouble to find out what is true and good, or when conscience is by degrees almost blinded through the habit of committing sin." In such cases, the person is culpable for the evil he commits.
Ignorance of Christ and his Gospel, bad example given by others, enslavement to one's passions, assertion of a mistaken notion of autonomy of conscience, rejection of the Church's authority and her teaching, lack of conversion and of charity: these can be at the source of errors of judgment in moral conduct.
When the Pope speaks definitively on fiath and morals, it is infallible. Many things have been declared infallible since 1870. The teaching barring birth control is one example. It was definitively declared by Pope Paul VI in the encyclical Humanae Vitae, which was written specifically for that purpose. Pope John Paul II wrote the encyclical Evangelium Vitae for a similar purpose--the bishops had asked him to clarify/codify Catholic teaching regarding life issues such as abortion and euthanasia. The Church's anti-abortion stance was also clearly published in the Catechism of the Catholic Church which is approved and released by the Vatican undr the direction of Pope John Paul II to clearly lay out that which the Chiurch considers to be core Catholic teachings. The Church's teaching against abortion is indeed infallible. You are correct in your understanding of what constitutes an infallible statement in regard to codifying as doctrine matters of traditional belief, such as the Assumption of Mary. But definitive statements from the Pope in regard to issues of faith and morals also morally obligate all Catholics and are both infallible and unchangable.